Two-speed transmission for helicopters



April 16, 1957 M. A. wAcl-ls TWO-SPEED TRANSMISSION FOR HELICOPTERS Filed Ap'ril 24, 1952 Y 2 Sheets-Sheet l mmm S ,Hy www Rw Tw o .R TA

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April 16, 1957 M A, WACHS TWO-SPEED TRANSMISSION FOR HELICOPTERS 2 Sheets-Sheet 2 Filed April 24. 1952 ATTORNEY United States PatentO TWO-SPEED TRANSMISSION FOR HELICOPTERS Miller A. Wachs, Stratford, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application April 24, 1952, Serial No. 284,189

1 Claim. (Cl. 74-750) This invention relates to apower transmission gear of the two-speed type having features especially adapting it for the transmission of power from the engine to the rotors of a rotary wing aircraft.

v It is an object of this invention to provide an improved transmission of this type in which the weight relative to the power transmitted is very low.

Another object of the invention is to provide a twospeed planetary type transmission in which the parts are designed to have la favorable strength-weight ratio.

A further object of the invention is to provide a change speed gearing of this type having improved hydraulically operated clutch mechanism for effecting the change from one speed to another. p

A still further object of the invention is to provide an improved construction for taking `out end thrust developed in the transmission by the hydraulic clutch mechanism.

A yet further object of the invention is generally to improve the construction and operation of change speed gearing for helicopter drives.

These and other objects of the invention will be evident or will be pointed out in connection with the description of the accompanying drawing which shows one embodiment of the invention for purposes of illustration.

In these drawings:

Fig 1 is a vertical section through a helicopter transmission embodying the invention;

Fig. 2 is a section on line 2--2 of Fig. 1; and

Fig. 3 is a section on line 3-3 of Fig. l.

Referring to Fig. 1, the transmission shown comprises a two-stage planetary gearing. The invention is concerned only with the first planetary stage and accordingly only this part of the transmission will be described in detail. The transmission is enclosed in a housing including a lower section and an upper section 12 connected together by a series of bolts 14 which extend through abutting flanges of the sections. The housing sections lll and 12 are divided by an intermediate wall 16 providing a lower annular chamber 18 in which the rst planetary stage is located and an upper annular chamber 20 which houses the second planetary stage.

Referring to the rst planetary stage, an engine driven shaft 22 is -journalled in the housing on anti-friction bearings 24 and 26 and a rotor driving shaft 28 coaxial therewith is journalled at its lower end in a bearing 30 which is piloted in the upper end of engine driven shaft 22. At ts'upper end shaft 28 is journalled in a bearing 32 in wall 16. The engine driven shaft 22 has an axial bore 34 which extends through a substantial portion of its length from which hydraulic fluid is conducted through passages 36 to aclutch hereinafter described. The rotor driving shaft 28 is also tubular, the axial passage 38 therethrough having an enlarged diameter upper end 40 in which an anti-friction thrust bearing 42 is disposed which bears against'a shoulder 44 in the passage through the shaft. A tension rod 46 extends through the bearing 42 and carries a nut 48 at its upper end which overlies the bearing 42. The lower end of rod 46 is screw threaded into the upper end of the engine driven shaft 22, thus providing a tension member connecting the coaxial engine driven and rotor driving shafts while permitting free relative rotation of the two shafts.

The engine driven shaft 22 carries a cup-shaped casing 5@ of relatively large diameter which as shown herein is integral with the shaft. Casing 50 carries an upper ring gear 52 and lower internal splines 54. The rotor driving shaft 28 has splined thereto a planetary spider 56 which carries a plurality of planetary pinions 58 rotatable on studs 60 fixed in spaced relation about the periphery of the spider. These planetary pinions engage the ring gear 52 and also engage a reaction gear 62 which surrounds shaft 28 and is journalled at its lower end in bearings 64 carried by the spider 56. The reaction gear 62 is` piloted at its upper end in a roller clutch 66 (Fig. 2) irl.E

62 is restrained against clockwise rotation as viewed in Fig. 2.

The spider 56 carries external splines '76 which are in the same planes as the lower internal splines 54 on the casing 50, the annular space between the splines 76 and 54 being occupied by ring-shaped clutch plates 78 and 80 arranged alternately in a stack with the plates 78 having splined engagement with internal splines 54 and the plates 80 having toothed engagement with the external splines 76. A ring-shaped piston 82 engages the lowermost plate of the stack and is movable axially in ia shallow cylinder 84 formed in casing 50 by an upstanding annular ange 51. Cylinder 84 communicates with passages 36 which supply fluid under pressure to move the piston axially against the stack of clutch plates. Above the stack an annular plate 85 transmits the thrust of the piston 82 to the spider 56, this thrust being transmitted through the roto-r driving shaft 28 to the thrust bearing 42 where it is resisted by tension rod 46 carried by the engine driven shaft 22.

The rotor driving shaft 28 carries a sun gear 86 which transmits the drive to the second stage of the planetary gearing. Since this gearing is a conventional planetary reduction gearing further description is not necessary for an understanding of the invention.

Engine driven shaft 22 carries a beveled gear 88 directly beneath the bearing 26 which meshes with a corresponding beveled gear on la trail rotor drive shaft 92. The latter shaft is used for driving the usual anti-torque rotor required in a helicopter of the type having a single lifting rotor.

It will be evident that when hydraulic fluid under pressure is admitted through the axial bore 34 of shaft 22v and through passages 36 into cylinder 814 beneath the piston 82, frictional engagement between the clutch plates 78 and 80 will effect a solid drive through the iirst stage of the planetary gearing, since casing Sii and the spider 56 are rigidly connected and no rotation of the planetary pini'ons about their own axes can take place. Thus casing 50, planetary spider 56, planetary pinions 58 and re-H will also rotate counterclockwise and reaction gear 62 will be rotated with the planetary pinions in a counterclockwise direction which is permitted by the one way drive clutch rollers 68 (Fig. 2). When the hydraulic pressure on the piston 82 is reduced to permit relative movement of the clutch plate 78 and 80 the counterclockwise rotation of casing 50 will result in a counterclock- Patented Apr. 16, 1957l wise` rotation of the planetary# pinions about their own axes.and. attendency. to` rotate.the reaction, gear 62- inar clockwise direction. This rotation of the latter gear, however, is resisted by engagement of the rollers 68 of the' roller clutch with.- cam` faces- 70 which results in rotationl of therotor driving shaft; 28 i-na= countercloclowise direction. but' at, ay lowerl speed'. The particular ratios; shown herein provide a reduction in speed? but this can be varied by the design of1 theY gearsV as is wellknown` infr the arti Itf will 'oenoted that since the reaction gear- 62; is required toA absorbonly the difference inthetorques being-exerted'y on the two shafts, this mem'- ber can be'relatively light" and" small in diameter with' ay consequent savi'ng in' weight and cost.

-In ai helicopter drive2 i'tis'rnotonly necessary to provideI forI driving the rotorU from the-enginebut itis also necessarytopermit the rotor tofreewheel in the same direction of* rotation in the event" that the engine fails. This isr` donew by providing a freewheeling roller clutchk (not shown) between the engine and the engine driven shaft' 22'; Further, with" the`Y twospeed planetary gearing shown,.it'is necessary to drive the tail rotor by the rotor during sucliy autorotation, both in high and' low speed' drives, in. order that the torque compensation of the tail.

rotorV may'notbe lost: In the high ratio drive in which the two shafts 22 and 28`V are in effect locked together by the clutch the tail rotor will rotate in the proper relationslii'p` to the rotor to; maintain torque equilibrium,l

butinv the` event ofv power failurein the lower gear when the clutch is disengaged means are provided in accordance with this' invention to drive the shaft 22 from the shaft 28 withv a 1'-1 ratio. To this endV a one-way roller clutch (Fig. 3). is provided in which the rollers. 94 areV grippedL between the inclined faces 96 andthe internal cylindricalv periphery 98 ofange 51.0n casingtwhenever the` shaft 28 tends to overrun shaft 22. It willbe.

evident that'theroller clutch does not interfere withthe. lower. ratio drive previously described whichis in effect.

when the clutch is.,disconnected,` since under. these. conditions the shaft 22 is overrunning the shaft 28, a condition permittedl by clutch rollers 94.

It will thusbe evident that as a result of this inven-r tion a two-speed gearing has` been provided which is especially adapted for use in helicopter drives inwhich two.very diverse conditions prevail. When-the.. helicopter is. hovering, eiciency demands a low tip speed of. thev vention, a particularly compact helicopter drivel mechanism has been provided which is light in weightL yet amply capable of. transmittingthe high powers nowl required of such. transmissions.

It will also. be. clear that the provision of the tension member. and. its thrustk bearing, disposed, within the axial boreof they rotor drivingshaft,I and the: eon11ection of:this tension member to. the motor driven shaft, provides a very.` compact. transmission in which. allvv ax-i'a-l thrust betweent the. alignedshafts. is takenout within; the structure witlrno appreciable;weightpenalty. TheV high prevailing thrust'load generated by the clutch is taken out by a very small and light thrust bearingbecause ofthe low relative speed of shafts 28v and 22? at. beginning ofclutch engagement-l which, reduces to; zeroI when: the clutch isv fully engage While only one embodiment of the invention has been shownand-describedherein it willA be evident' that various constructions and arrangements of the parts may be made without departing from the scope of the invention.

I claim:

In a rotary wing aircraft, a main sustaining rotor, an engine driven shaft, a rotor driving shaft, transmission means for driving said rotor drivingA shaft from said. en.- gineY driven shaft in powered" ffight, said transmission means. including. a.7 support, said` engine driven shaft hav-Y cup-shaped casing'conn'eteda thereto, said rotor driving shaft extending into said cup-shaped casing, a; reaction member adjacent to and surrounding said rotor driving shaft and extending" into saidv cup-shapedr casing, said reaction member having af gear thereon;` a planetary pinion carrier connected to said rotor driving shaft between said reaction member and the end of said engine driven shaft, planetary pinions on said carrier, said cup-shaped casing having a iirstfinternal ring'gea'r with teeth around its side, said? planetary' pinions meshing with the'. teeth ofn said tirstl' internat` ringA gearA onA said cup-shaped casing and the gear on said reaction member, a one-Way clutch between said' reaction gear and' said support for' locking saidy reaction1 gear against rotation in a direction.

opposite to the rotationl of said engine' driven shaft, external splines on said carrier below said' pinions', internal splines on said cup-shaped'. casing.. between the'- teeth:

of said first internal ring' gear' and' thebottom of' said' splines of said carrier;A thek otherperipheral' Wall facingn said'f'rst wall'being formed by the internalsplinesron said cup-shaped casing, one annular wall'beingformed on/said carrier and extending outwardly from said' carrier at a.

point at one end of said` external splines to a. point adjacentto said second internal splines, the other annular wall being formed by'theV face of an annular piston,vsaid piston being slidably mounted in an annular cylinder formed in the'- bottom of said cup-shaped casing, a multiplicity of annular clutch plates being located in said' annular charnber, alternate clutchplates havinginner teeth ixedlyl meshing within said external splines, theremainingclutch plates havingexternal teeth xedly meshing, within said internal splines, hydraulic means for moving said piston towardI said` other annular wall to place said clutch plates intoI active engagement, said last named means including a passageway through said engine driven. shaft and said cup-shaped casing, said passageway terminating` behind said piston in the annular, cylinder, formedY in` the bottom of said cup-shaped casinga tension member connected'to saidrotor driving shaft and to said engine driven shaft', said tension member preventingl axial movementy between said shafts caused by the movement of said piston.

References Cited in the; file: of: patent` UNITED STATES PATENTS 1,933,424 Forsyth Oct. 3l, 1933. 2,225,121. Lundqui'st .Deol'l, 1940 2,348,716 Banker May` 16,1944 2,388,455 White Nov. 6, 19.45 2,396,038 Bossi Mar. 5-, 1946` 2,531,032 Desmoulins Nov. 21, 1950 2,648,386 Tidd Aug. 11, 1953 FOREIGN. PATENTS 824,304 Germany "Dec, 1'0, 19'51 

